1. Field of the Invention
The present invention relates to an electron beam irradiation device to irradiate an electron beam to an irradiated object which passing an irradiation chamber while introducing inert gas in the irradiation chamber.
2. Description of the Related Art
There is known an electron beam irradiation device to irradiate an electron beam to a belt-shaped irradiated object such as a resin film and to conduct a processing such as bridging, hardening or reforming to the irradiated object. In this kind of irradiation device, when the electron beam is irradiated under the environment in which oxygen is exist, the inconvenience which the oxygen reacts to the electron beam and the irradiation energy of the electron beam is used sometimes occur. Therefore, as described in JP-B 63-8440, JP-A 5-60899 and JP-U 6-80200 for example, inert gas such as nitrogen is introduced in the irradiation chamber of the electron beam, and the oxygen is substituted for the inert gas, thereby the oxygen concentration in the irradiation chamber is restrained in a low level (less than 100 ppm, for example).
However, in the above-described electron beam irradiation device, the inert gas is continuously supplied in a constant flow rate, thus the quantity of the inert gas consumed is grate, and sometimes excess inert gas is introduced. For example, in the electron beam irradiation device of the type which irradiates an electron beam while making the irradiated object travel, the air which is going to enter the irradiation chamber accompanying the irradiated object is need to be removed out of the irradiation chamber by stripping it off with the inert gas, for that purpose, at the entrance of the irradiation chamber, a large quantity of the inert gas must be bowed to the irradiated object continuously. However, when the irradiated object is stopped or when the irradiated object is traveled for an arranging operation at a speed lower than when the electron beam is irradiated, the involving of the accompanying air does not exist or even if it exists the influence is small, therefore, if the inert gas is continuously introduced at the same flow rate as when the electron beam is irradiated, the inert gas is consumed vainly.